1. Field of the Invention
The present invention relates, generally, to apparatus and methods used in the packaging industry. More particularly, the invention relates to apparatus and methods for folding flaps of cartons traveling in a continuous stream. The invention has particular utility in folding the major flap of a six-sided carton while maintaining the relatively squared corners of the carton.
2. Background Information
The state of the art includes various devices and methods for folding flaps of cartons traveling on a continuous carton conveyor. These devices include stationary plows and rotary tuckers. U.S. Pat. No. 5,036,644, assigned to applicant's assignee, illustrates a stationary plow; and U.S. Pat. Nos. 5,456,058, 5,457,940, and 5,241,806, all assigned to applicant's assignee, illustrate rotary tuckers.
These devices and methods are believed to have significant limitations and shortcomings. These limitations and shortcomings are especially evident when the known art attempts to fold the major flaps found in the bottom of six-sided cartons. Although stationary plows work well for folding small flaps, they tend to skew six-sided cartons when they attempt to fold the major flap. These cartons are stored and loaded into a carton magazine in a relatively flat shape. The six-sided cartons have a tendency to skew away from a rectangular footprint and back toward their original flat shape after they have been erected on a carton conveyor. The size of the major flaps is another factor that significantly affects the skewing problem. When a carton moves longitudinally over a stationary plow designed to laterally fold the major flap, the plow produces a resultant force. The lateral component of the resultant force folds the flap. However, the longitudinal component of the resultant force pushes the flap of the carton back against the longitudinal flow of the cartons and skews the cartons. Larger flaps cause the stationary plows to induce larger longitudinal component forces, which cause a greater tendency to skew the cartons when the flap is folded.
Rotary flap tuckers are typically used to fold dust flaps or end flaps found on the side of the carton. These flaps are longitudinally folded either with or against the flow of the stream of cartons. However, the major flap of the six-sided cartons are folded in a direction lateral to the flow of the stream of cartons. Therefore, these rotary flap tuckers would have to be adapted to laterally fold these bottom flaps. However, these stationary rotary flap tuckers would either have to operate at a speed that exerts considerable force on the cartons and thus skews the cartons, or they would require the cartons to travel at a lower speed or with intermittent motion.
Applicant's invention provides a package squaring device, or flap lifter, which overcomes the limitations and shortcomings of the known art. Specifically, it acts as a moveable plow that longitudinally travels along side of the cartons and produces a gentle lateral force to fold the flaps. Therefore, the package squaring device does not create the resultant forces that tend to skew the cartons.